Ron Guth:
The 1909-S Half Dollar is a semi-scarce date that is on par with the 1909-O but with a few more higher-end examples. The most frequently-seen Mint State grade is MS64. Gems and MS66's are fairly plentiful and there are a handful of MS67 examples for the quality-conscious buyer. The finest 1909-S Half Dollar is the PCGS MS67+ (formerly NGC MS68) from the Hugon and Shireman collections.

The 1909-S Inverted S is one of the few varieties in the Barber Half Dollar series. It was created when the engraver punched the mintmark upside-down into the die. This is a fairly subtle error that, once seen, is rather obvious (see the variety illustration above).